The forbidden transition M1 between the ground state 7S1/2 and the excited state 8S1/2 only appears due to mixtures between the hyperfine states and relativistic corrections. At TRIUMF, Canada's subatomic physics laboratory, we have managed to measure and characterize this transition, necessary to look for the E1 transition between the same states but due to the weak force, that causes parity non conservation (PNC). It is necessary to produce the francium atoms in a nuclear reaction and then proceed to their trapping, cooling and confinement within a Fabry Perot cavity in order to excite this transition which is at least ten orders of magnitude less likely than the D2 line in the same atom (7S1/2 to 7P3/2).

Work done as part of the FrPNC collaboration.